The increased number of tunnels constructed in the past several decades has substantially enhanced tunneling technology and equipment. Tunneling equipment has progressed to the extent that approximately 200 feet per day can be frequently tunneled through relatively soft rock using a tunnel boring machine. Tunnels for vehicular and pedestrian traffic are becoming more popular, and recently constructed tunnels bore through increasingly longer lengths of earth. Tunneling techniques are also finding increased acceptance for various product or service transmission lines or cables. Proposed subterranean tunnels for atomic accelerators far exceed the practical technology available for their construction.
In most cases, a shaft or tunnel is not complete until a lining has been placed along the perimeter of the bored hole. Although liner placement frequently is a significant portion of the total cost of a tunneling project, improvements relating to tunnel boring machines have exceeded the capability of tunnel lining technology. Fixed cylinder "slip" or "jump" form linings have been used for decades for tunnel lining, and precast liners are widely used. Both of these techniques, however, are slow and labor intensive. Moreover, slip or jump form lining techniques pose considerable engineering problems, including limited advance speed, rapid wear, large propulsion equipment, and induced cracks in the extruded concrete linings. These significant engineering problems, in turn, are all directly or indirectly due to large frictional forces between the machine and the concrete tunnel walls.
A remote shotcrete shaft lining system has been developed for lining substantially vertical bore shafts. Modular segment assemblies supported by a wire rope are lowered into a borehole during shotcrete application, and the shotcrete lining is applied in a helical pattern. A slip form for applying a vertical shaft lining is also disclosed in U.S. Pat. No. 4,205,949. These techniques are, however, practically limited to lining vertical shafts, and are inherently expensive.
An extruded tunnel lining system has also been developed under sponsorship from the Department of Transportation and the Urban Mass Transit Administration. This system delivers concrete to the annulus behind a slip from, and the form advances at a steady rate with the exposed concrete behind the slip form being self-supporting. Although various techniques have been devised to try to reduce the force required to move the slip form, this technique suffers substantially from the inherent drag associated with trying to slide a lining along loosely formed or forming concrete.
Another slip form system referred to as a continuous lining system has been developed under sponsorship from the Department of Transportation. This system lines shafts from the top down, and otherwise operates in a manner similar to the extruded tunnel lining system. U.S. Pat. No. 4,270,876 also discloses techniques for lining a vertical mine shaft with concrete. Additional information regarding advancement in tunnel lining techniques are described in the article entitled "Advanced Techniques for Rapidly Placing Concrete Linings in Tunnels and Shafts".
A variant of an extruded tunnel lining system is the tunnel drive shield system, as disclosed in U.S. Pat. Nos. 4,265,565 and 4,334,800. This system, which is primarily used for temporary tunnel support, utilizes a hydraulic advance ram to move an elongate member in a longitudinal direction relative to a support frame.
Various other techniques have been devised for decreasing the labor and expense associated with forming shaft linings. U.S. Pat. No. 4,222,681 discloses a tunnel shield machine utilizing a device for absorbing the thrust force from a drive mechanism and transmitting that force to the concrete tunnel, while another version of a tunnel shield machine is disclosed in U.S. Pat. No. 4,332,508. U.S. Pat. No. 4,437,788 discloses techniques for forming a continuous concrete wall in tunnels or galleries, and a drive shield machine including a plurality of cutters is disclosed in U.S. Pat. No. 4,482,270. U.S. Pat. No. 4,316,701 discloses techniques for stripping off suitably interconnected vault segments of a liner, and U.S. Pat. No. 4,451,176 discloses a tunnel lining produced by spraying concrete rearwardly between the spaces of a multipart framework. None of these techniques have, however, been widely accepted because of increased costs, high labor, and relatively slow progress rate for such tunnel lining techniques.
The disadvantages of the prior art are overcome by the present invention, and improved methods and apparatus are hereinafter described for forming concerte liner in a tunnel or shaft.